1. Field of the Invention
This invention relates, generally, to methods for repeating prerecorded digital audio material or any other digital bitstream. More particularly, it relates to methods for modifying conventional compact disc players to achieve a program repeater function, and to the products of such methods.
2. Description of the Prior Art
Research has shown that businesses can effectively convey advertising and informational messages by playing such material over the public address system while customers are on their premises. Additionally, businesses have found that playing such messages while telephone callers are "on hold" is also effective. These messages might be delivered by a store manager or other personnel, but the cost of such personally delivered, real time advertising is quite high, and there is no way to control the quality of the "performance" of the message.
Accordingly, businesses have adopted the use of prerecorded messages that are continuously played; music is frequently placed in the background to break up the monotony of the spoken voice. Since the prerecorded message is repeated endlessly, devices for playing them are called "program repeaters."
There are numerous other applications for program repeaters. Moreover, the material that is repeated need not be audio data, i.e., there are numerous applications that call for repetition of different types of data streams.
A typical program repeater employs the well known audio cassette tape. For various reasons, such systems produce less than ideal results. The typical cassette tape has a thirty minute maximum capacity per side; thus, the operator is required to rewind the tape every half hour to provide long-term play. More advanced players have an automatic rewind function, but the time spent in rewinding produces a period of silence in the store or over the phone line. Two methods for avoiding the necessity of constant human attendance and rewind time have been developed. Some currently available players automatically reverse themselves and play the opposite side of the tape without human intervention and without any rewinding. Endless- or continous-loop tapes are employed to acheive the same result.
Regardless of which of the above-described methods is employed, due to the physical contact between the tape and the machine's heads and the resultant wear, the lifetime of a continuously-played tape is unacceptably short. Additionally, the maximum length of endless-loop tapes, and hence their playing cycle, is unacceptably short.
Program repeaters are also used to repeat video material. Generally, the same methods described above with respect to audio cassette tapes are available to repeat material on videotapes. In some cases, video tapes are employed to repeat audio-only material. Tapes in video cassette players last longer than audio cassette tapes because the tape surface does not come into physical contact with the tape heads, but the lifetime of an endlessly repeated video tape is still unacceptably short due to the physical wear of endless play.
Finally, there is an additional drawback common to many tape-based program repeaters, whether videotape- or audiotape-based. Many players, upon loss of power, will not automatically re-start themselves when a power is restored. The result is that, when power is interrupted, a not uncommon occurrence, an operator must reset the program repeater. In addition, since operating personnel typically cannot monitor what is being played to telephone callers on hold, a program repeater used for this purpose may be nonfunctional for an extended time before anyone in the business realizes it.
Recent advances in technology have led to the development of program repeaters employing memory chips (typically Dynamic Random Access Memory chips) to store and repeat the program material. Such devices, essentially lacking any moving parts, are free of the physical wear and tear characteristics of the previously-described devices. However, the storage capacity of a reasonably inexpensive DRAM-reliant device is only a few minutes. The sampling rate employed to digitize the audio material for chip storage is typically relatively low, resulting in distortion and poor audio quality. The sampling rate may be increased, but this results in a corresponding reduction in program duration. To allow both a high sampling rate and adequate program length, given the prevailing costs of DRAM memory chips, the amount of memory required would result in an unacceptably high device cost. Still, because of the lack of physical wear, DRAM is currently the technology of choice for program repeaters.
Compact disc players are digital devices that include a source of laser radiation that is directed onto a rotating disc containing digital information. Since the radiation used to read the disc does not cause deterioration, the disc will last indefinitely. The audio quality of CD is unparalleled. CD players are widely available at a reasonable cost, and enjoy high longevity and reliability. These characteristics suggest that compact disc players might be a favorable choice for use as program repeaters.
However, a conventional compact disc stores a maximum of 74 minutes of audio material. In order to acheive continuous play, an operator must restart the player many times during a day. More expensive players may be set to continuously repeat a single disc track or an entire disc. A few players may even allow a sequence of tracks to be programmed to repeat continuously.
However, in the event of a power failure, all CD players lose their play settings and will not automatically reactivate themselves upon restoration of power. Therefore, similar to the situation described previously with respect to tape-based program repeaters, in the event of a power failure, a conventional CD player will lose its settings inadvertently and remain nonoperational for indefinite periods of time until the problem is discovered.
Additionally, the characterisic described in the foregoing paragraph prevents the use of a timer to supply power to the CD player at the beginning of each business day and allow the program repeater to begin functioning automatically. If it is desired that the player run only during limited hours, an operator must set the player in its desired play sequence each day. To avoid such constant operator attention, a conventional CD player must be left on continuously. Its lifespan is therefore unnecessarily shortened.
Thus, according to those of ordinary skill in the field, the future lies in DRAM based devices; the conventional wisdom is that with the passage of time, inventors will eventually produce DRAM chips with increased capacity at lower costs, and that DRAM-based devices will then be perfectly acceptable as program repeaters. Significantly, the conventional wisdom has written off audio and video cassettes and compact disc players for the reasons given above.
Clearly, then, when the prior art is viewed as a whole as required by law, there is no indication that the future of program repeaters lies with compact disc players. Just as importantly, nothing in the art suggests how a conventional compact disc player could be modified to reactivate itself in the event of a power failure. Even more importantly, the very suggestion that a compact disc player could be modified to reactivate itself upon restoration of power after an interruption is not found in the prior art.